1. Field of the Invention
The embodiments of the invention generally relate to a method and apparatus for plasma processing a substrate, and more specifically, a plasma processing system having at-electrode RF matching, and a method for processing a substrate using the same.
2. Description of the Related Art
Large area substrates are often utilized in the manufacture of solar cells and liquid crystal displays. Liquid crystal displays (LCDs) or flat panels are commonly used for active matrix displays such as computers, touch panel devices, personal digital assistances (PDAs), cell phones, television monitors, and the like. Further, organic light emitting diodes (OLEDs) have also been widely used for flat panel displays. Generally, flat panels comprise two plates having a layer of liquid crystal material sandwiched therebetween. At least one of the plates includes at least one conductive film disposed thereon that is coupled to a power source. Power, supplied to the conductive film from the power supply, changes the orientation of the crystal material, creating a patterned display.
Solar cells may be formed from crystalline material or from amorphous or micro-crystalline materials. Generally, there are two major types of solar cells that are produced in large quantities today, which are crystalline silicon solar cells and thin film solar cells. Crystalline silicon solar cells typically use either mono-crystalline substrates (i.e., single-crystal substrates of pure silicon) or a multi-crystalline silicon substrates (i.e., poly-crystalline or polysilicon). Additional film layers are deposited onto the silicon substrates to improve light capture, form the electrical circuits, and protect the devices. Suitable substrates include glass, metal, and polymer substrates. Thin film silicon solar cells have gained a significant market share due to low-cost, large-area deposition of the amorphous-microcrystalline silicon absorber layers. Thin-film solar cells use thin layers of materials deposited on suitable substrates to form one or more p-n junctions, which facilitate current flow within the cell when exposed to light.
In order to manufacture these displays and solar cells, a substrate, such as a glass or polymer workpiece, is typically subjected to a plurality of sequential processes to create devices, conductors and insulators on the substrate. Each of these processes is generally performed in a process chamber configured to perform a single step of the production process. In order to efficiently complete the entire sequence of processing steps, a number of process chambers are typically coupled to a transfer chamber that houses a robot to facilitate transfer of the substrate between the process chambers. One example of a processing platform having this configuration is generally known as a cluster tool, examples of which are the families of AKT plasma enhanced chemical vapor deposing (PECVD) processing platforms available from AKT America, Inc., of Santa Clara, Calif.
As demand for flat panels and solar cells has increased, so has the demand for larger sized substrates. For example, large area substrates utilized for flat panel fabrication have increased in area from 550 mm by 650 mm to over 4 square meters in just a few years and are envisioned to continue to increase in size in the near future. This growth in the size of the large area substrates has presented new challenges in handling and production. For example, the larger surface area of the substrates has resulted in increased RF power requirements, which in turn, has increased the size and cost of RF power transmission components. Since the equipments size and power consumption of processing equipment suitable for large area substrates and conventional semiconductor wafers differ by orders of magnitude, mere scale-up of conventional solutions does not provide acceptable or in some cases even predictable results, thus demanding new innovations to enable next generation process and equipment.
Therefore, there is a need for an improved plasma processing system suitable for processing large area substrates.